Auto-switching system for switch-over of gas storage and dispensing vessels in a multi-vessel array

ABSTRACT

A gas storage and dispensing system, including multi-vessel arrays of gas dispensing vessels that require successive change-over to provide ongoing supply of gas to a gas-consuming process, with a pump coupled in gas flow communication with the array. The system is provided with capability for time delay auto-switchover sequencing of the switchover operation in which an endpoint limit sensing of an on-stream gas dispensing vessel is responsively followed by termination of gas flow to the pump, inactivation of the pump, autoswitching of vessels, reinitiation of gas flow to the pump and reactivation of the pump. The system minimizes the occurrence of pressure spikes at the pump outlet in response to pressure variation at the pump inlet incident to switchover of gas supply from one vessel to another in the multi-vessel array.

FIELD OF THE INVENTION

The present invention relates generally to gas storage and dispensingvessels, and particularly to multi-vessel arrays that require successivechange-over to provide ongoing supply of gas to a gas-consuming processunit. In a specific aspect, the invention relates to a gas cabinetcontaining multiple gas storage and dispensing vessels providing gas tosemiconductor manufacturing tools in a semiconductor manufacturingfacility, and to auto-switching systems for switch-over of vessels tomaintain continuity of gas dispensing operation.

DESCRIPTION OF THE RELATED ART

The physical adsorbent-based gas storage and dispensing system disclosedin Tom et al. U.S. Pat. No. 5,518,528 has revolutionized thetransportation, supply and use of hazardous gases in the semiconductorindustry. The system includes a vessel holding a physical adsorbentmedium such as molecular sieve or activated carbon, having sorptiveaffinity for the gas that is to be stored in and selectively dispensedfrom the vessel. The gas is held in the vessel in an adsorbed state onthe sorbent medium at reduced pressure relative to a corresponding empty(of sorbent) vessel holding an equivalent amount of gas in the “free”(unadsorbed) state. Advantageously, the interior gas pressure in thestorage and dispensing vessel is at sub-atmospheric pressure, oratmospheric or low superatmospheric pressure.

By such reduced pressure storage, the safety of the gas storage anddispensing operation is substantially improved, since any leakage willresult in a very low rate of egress of gas into the ambient environment,relative to a conventional high-pressure gas storage cylinder. Further,the low pressure operation of the adsorbent-based system, is associatedwith a lower likelihood of such gas leakage events, since the reducedpressure reduces the stress and wear on system components such asvalves, flow controllers, couplings, joints, etc.

In application to semiconductor manufacturing operations, the gasstorage and dispensing vessels of the foregoing type are frequentlydeployed in gas cabinets, in which a plurality of vessels is manifoldedto appropriate flow circuitry, e.g., including piping, valves,restricted flow orifice elements, manifolds, flow regulators, mass flowcontrollers, purge loops, instrumentation and monitoring equipment, etc.Such flow circuitry may be associated with automatic switching systemsthat permit a gas storage and dispensing vessel to be taken off-streamwhen it is exhausted of gas or otherwise approaching empty status, e.g.,by appropriate switching of valves, so that the exhausted or otherwisesubstantially depleted vessel is isolated from gas feed relationshipwith the flow circuitry, to facilitate change-out of the vessel.Concurrently, a full gas storage and dispensing vessel is switched on,e.g., by appropriate switching of flow control valves in a manifold toplace such fresh vessel into gas feed relationship with the flowcircuitry. The isolated depleted vessel then can be uncoupled from theflow circuitry and removed from the gas cabinet, to enable installationof a full vessel for subsequently switch-over usage of such vesselduring the ensuing operation when the previously switched-on vessel hasbecome depleted of gas.

In addition to the gas storage and dispensing vessels of the foregoingtype as described in Tom et al. U.S. Pat. No. 5,528,518, commercializedby ATMI, Inc. (Danbury, Conn., USA) under the trademarks SDS® and SAGE®,fluid storage and dispensing vessels described in U.S. Pat. Nos.6,101,816; 6,089,027; and 6,343,476 issued to Luping Wang, et al. andcommercially available from ATMI, Inc. (Danbury, Conn., USA) under thetrademark VAC are likewise deployed in gas cabinets in semiconductormanufacturing facilities and require periodic switching to maintaincontinuity of gas dispensing operation. The VAC® vessels feature a fluidpressure regulator that is disposed upstream of a flow control elementsuch as a flow control valve, whereby gas dispensed from the vessel isdispensed at a set point pressure determined by the regulator. The fluidin the VAC® vessel can be a high-pressure liquid or gas that is confinedagainst the regulator, as a source of gas for the semiconductor process.The regulator can be interiorly disposed in the vessel to protect theregulator against impact or environmental contamination, and the vesselmay in specific embodiments contain physical adsorbent material fordesorptive dispensing of gas from the vessel. By providing the regulatorwith a set point pressure level that is sub-atmospheric, atmospheric orlow superatmospheric pressure, the same operating and safety advantagesare realized as described hereinabove in connection with the gas storageand dispensing vessels of U.S. Pat. No. 5,518,528.

Vessels of the foregoing type, commercialized under the SDS®, SAGE® andVAC® trademarks, when employed to contain fluid at low pressures,produce gas that in many applications must be boosted in pressure torender the gas amenable to subsequent usage. In such instances, anextractor system can be utilized to extract gas from the vessel. Theextractor system includes an extraction pump and a surge tank, alongwith controls and safety systems essential to the safe operation of thegas supply arrangement. The extractor system is housed in an exhaustedand monitored metal enclosure, with gas delivery hardware being housedin a main cabinet, and control electronics being located in a separateenclosure that may for example be mounted on the top of the maincabinet. Multiple gas storage and dispensing vessels can be contained ina separate dedicated gas cabinet containing gas delivery hardware, as areduced pressure module with which the extractor system can be coupledto provide constant pressure delivery of gas to a semiconductor tooloperating at mild vacuum conditions. The reduced pressure module maycontain heating capability to heat the gas dispensing vessels tofacilitate the dispensing operation.

In the reduced pressure module, the gas dispensing hardware andelectronics can be programmably arranged to effect automatic vesselchangeover at a preset pressure, when a first vessel reaches a point ofdepletion at which it is no longer able to maintain the preset pressure.For such purpose, the gas dispensing hardware and electronics can beconstructed and arranged for automated or manual evacuation, purging andleak detection of the gas flow path. A programmable logic controller(PLC) can be used in the system for monitoring valve status, systempressures, vessel weights and temperatures, and for providingpreprogrammed sequences for control of the following functions: vesselchange-out, initiating gas flow, auto-switchover of vessels, purge gascontrol, process/purge gas evacuation, securing process gas flowfollowed by shut-down, and temperature control of vessel heaters, e.g.,heating blankets.

Reduced pressure modules and extractor systems of the above-describedtype are commercially available from ATMI, Inc. (Danbury, Conn., USA)under the trademark RPM.

Thus, vessels of the foregoing adsorbent-based and/or internal pressureregulator-equipped types can be deployed in multi-vessel arrays, inwhich automatic switch-over of vessels, from a depleted vessel to a fullvessel, takes place when the end point of an active (on-stream) vesselis reached. The end point may be determined in various ways—it may bedetermined by a decline in dispensed gas pressure and/or flow rateindicative of depletion of the vessel contents, or it can be determinedby weight loss of the vessel incident to continued dispensing of gastherefrom, or by cumulative volumetric flow of dispensed gas, or bypredetermined operating time, or in other suitable manner.

Regardless of the means or mode of determining end point of the vessel,the automated switching from a depleted vessel to a full one involves adrastic change in pressure at the inlet of the pump that is employed asa motive fluid driver to effect flow of gas through the flow circuitryto the downstream gas-consuming process. The proportional integralderivative (PID) control logic that is employed with the pump in a usualarrangement cannot react quickly enough to slow the pump to avoid theimpact of the pressure change, so that a pressure spike occurs as aresult at the outlet of the fast running pump. In a sub-atmosphericpressure system, e.g., as employed for ion implantation in whichsub-atmospheric operation of the implant chamber represents an optimalprocess arrangement, this pressure spike can cause pressure to exceedsystem set point limits. Such overpressure condition in turn can causealarms to be actuated, and in an extreme pressure variation condition,the safety monitoring elements of the gas delivery system may causeshut-down of the gas flow and undesired stoppage of the downstreamgas-consuming process.

It would therefore be an advance in the art to provide an automatedswitching apparatus and method for gas delivery systems comprisingpumping/extractor apparatus coupled with multiple vessel arraysincluding vessels of the type described in the aforementioned U.S. Pat.Nos. 5,518,528; 6,101,816; 6,089,027; and 6,343,476, which minimizepressure perturbations incident to vessel switching.

SUMMARY OF THE INVENTION

The present invention relates generally to gas storage and dispensingvessels, and particularly to multi-vessel arrays that require successivechange-over from an exhausted vessel to a fresh gas-containing vessel inthe array, in order to provide ongoing supply of gas to a gas-consumingprocess.

The invention relates in one aspect to a gas supply and dispensingsystem, comprising:

-   -   an array of at least two gas storage and dispensing vessels        arranged for sequential on-stream dispensing operation involving        switchover from a first vessel to a second vessel in the array;    -   a pump coupled in gas flow communication with the array for        pumping of gas derived from an on-stream one of the vessels in        the array, and discharge of pumped gas;    -   an auto-switchover system constructed and arranged to sense an        endpoint limit of the on-stream one of the vessels and to        inititate auto-switching from the on-stream one of the vessels        to another of the vessels in the array having gas therein, for        subsequent dispensing of gas from said another of the vessels,        as a subsequent on-stream vessel,    -   wherein the auto-switchover system between sensing of the        endpoint limit and initiating auto-switching terminates flow of        gas to the pump and inactivates the pump; and    -   wherein the auto-switchover system after initiating        auto-switching reinitiates flow of gas to the pump and        reactivates the pump.

In another aspect, the invention relates to a method of substantiallyreducing pressure variation of pumped gas discharged from a pump in agas supply and dispensing system comprising an array of at least two gasstorage and dispensing vessels arranged for sequential on-streamdispensing operation involving switchover from a first vessel to asecond vessel in the array, wherein the pump is coupled in gas flowcommunication with the array for pumping of gas derived from anon-stream one of the vessels in the array, and discharge of pumped gas,

-   -   such method comprising:    -   sensing an endpoint limit of the on-stream one of the vessels        and switching from the on-stream one of the vessels to another        of the vessels in the array having gas therein, for subsequent        dispensing of gas from said another of the vessels, as a        subsequent on-stream vessel,    -   terminating flow of gas to the pump and inactivating the pump,        wherein said terminating and inactivating steps are conducted        between the step of sensing of the endpoint limit and the        switching step; and    -   reinitiating flow of gas to the pump and reactivating the pump,        wherein said reinitiating and reactivating steps are conducted        after the switching step.

Other aspects, features and embodiments of the present invention will bemore fully apparent from the ensuing disclosure and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of a reduced pressure module gas delivery systemwith vessel switchover capability according to one embodiment of theinvention.

FIG. 2 is a schematic of the flow circuitry of the reduced pressuremodule of FIG. 1.

FIG. 3 is the “MAIN MENU” screen display for the reduced pressure moduleof FIG. 1.

FIG. 4 is the “LEFT CYLINDER MENU” screen display for the reducedpressure module of FIG. 1.

FIG. 5 is a gas supply vessel change screen display for the reducedpressure module of FIG. 1.

FIG. 6 is a screen display of the “MAINTENANCE MENU” for the reducedpressure module of FIG. 1, which includes touch selections for “L/CMAINTENANCE MENU,” “R/C MAINTENANCE MENU,” “ANALOG CALIBRATION,” “MANUALCONTROL,” “CURRENT ALARMS,” “OPERATING PARAMETERS” and “MAIN MENU,”wherein “L/C” means Left Cylinder and “R/C” means Right Cylinder.

FIG. 7 is a screen display of the “STATUS SCREEN” for the reducedpressure module of FIG. 1, displaying the status of all valves in thereduced pressure module, the “GAS ON” or “GAS OFF” state of each gassupply vessel in the reduced pressure module, the pressure reading ofeach pressure transducer in the reduced pressure module, and thetemperature of each of the gas supply vessels.

FIG. 8 is a “Left Cylinder Gas On” screen display for the reducedpressure module of FIG. 1.

FIG. 9 is a PreChange Leak Test screen display for the reduced pressuremodule of FIG. 1, showing a schematic depiction of the gas panel,including valve states and pressure transducer pressure level, as wellas the elapsed time and the total time of the Leak Test.

FIG. 10 is a Local Purge Cycle screen display for the reduced pressuremodule of FIG. 1.

FIG. 11 is a cylinder change screen display for the reduced pressuremodule of FIG. 1.

FIG. 12 is a Post Cylinder Change Leak Test screen display for thereduced pressure display module of FIG. 1.

FIG. 13 is a Post Change Purge screen display for the reduced pressuremodule of FIG. 1.

FIG. 14 is a “Tool Evacuation” screen display for the reduced pressuremodule shown of FIG. 1.

FIG. 15 is a “Tool Purge” screen display for the reduced pressure moduleof FIG. 1.

FIG. 16 is a “Tool Pump Purge” screen display for the reduced pressuremodule of FIG. 1.

FIG. 17 is a “Local Evacuation” screen display for the reduced pressuremodule of FIG. 1.

FIG. 18 is a “Local Pump Purge” screen display for the reduced pressuremodule of FIG. 1.

FIG. 19 is a front elevation view of an extractor module according toone embodiment of the invention, such as may be employed in combinationwith the reduced pressure module of FIG. 1.

FIG. 20 is a front view of a portion of the extractor module of FIG. 19,showing the surge tank and extractor pump components thereof.

FIG. 21 is a “Status Screen” for the extractor module of FIG. 19,showing the flow circuitry of the manifold in the extractor module, andthe components of the extractor module.

FIG. 22 is a “Pump Control” screen display for the extractor module ofFIG. 19.

FIG. 23 is a schematic block diagram of an integrated semiconductormanufacturing facility showing the reduced pressure module (RPM) joinedin gas flow communication with an extractor module (EXTRACTOR) which inturn is coupled in gas flow communication with a semiconductormanufacturing gas-consuming unit (TOOL), with each of RPM, EXTRACTOR,and TOOL being joined in exhaust relationship with scrubber unit(SCRUBBER).

FIG. 24A and FIG. 24B show a process flow diagram including stepsinvolved in a time delay auto-switchover sequence according to oneembodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION, AND PREFERRED EMBODIMENTS THEREOF

The present invention provides an automated switching apparatus andmethod for gas delivery systems in which pumping/extractor apparatus iscoupled with multiple vessel arrays including vessels of the typedescribed in the aforementioned U.S. Pat. Nos. 5,518,528; 6,101,816;6,089,027; and 6,343,476.

The present invention is based on the discovery that the adversepressure effects of switch-over of fluid storage and dispensing vesselsin a multi-vessel array can be eliminated by the provision of a timedelay in the automated change-over system, to allow the pumpingcomponents to be signaled in advance of the automated change-over, sothat the pumping components responsively operate to prevent thetransmission of a pressure spike to the inlet of a fast-running pumpthat is employed to effect flow of gas through the flow circuitry to thedownstream gas-consuming process.

FIG. 1 is a front view of a reduced pressure module gas delivery system10 with vessel switchover capability according to one embodiment of theinvention.

The gas delivery system 10 is comprised of a main cabinet 12 as aprimary enclosure, and an electronics enclosure 26, wherein the maincabinet and the electrical enclosure are bolted together to form theintegrated gas delivery system. A gas supply manifold and the gas supplyvessels are housed within the main cabinet 12, which may for example beconstructed of 12-gauge cold rolled steel. The main cabinet 12 featuresleft hand door 14 with latch 18 and viewing window 22, and right handdoor 16 with latch 20 and viewing window 24. The electronics enclosure26, featuring on/off switch 28, is mounted on top of the main cabinet12, as illustrated. A touch screen interface 30 is located on the frontof the electrical enclosure on top of the cabinet.

The electronics enclosure 26 includes a programmable logic controller(PLC) for control of the integrated gas delivery system via the touchscreen interface 30, with communication between the PLC unit and thetouch screen being effected via a serial port connection on the PLCunit. The screen has a touch sensitive grid that corresponds to text andgraphics and communicates commands to the PLC unit. The touch screendisplays user menus, operational and informational screens and securitybarriers to facilitate only authorized access to the system.

The main cabinet 12 contains a pair of sorbent-holding gas storage anddispensing vessels, wherein the sorbent medium is provided in the formof a bed of particles of solid-phase physical sorbent having sorptiveaffinity for the gas in the vessel. In addition to the gas storage anddispensing vessels, the main cabinet contains the process flowcircuitry, which also includes piping, valving, etc. for purge andventing operations.

The gas supply vessels, sometimes hereinafter referred to as cylinders,may be of any suitable type. Although illustratively described herein assolid-phase physical adsorbent-containing vessels having gas thereinsorptively retained on the solid-phase physical adsorbent, e.g., amolecular sieve, activated carbon, silica, alumina, sorptive clay,macroreticulate polymer, etc., it is to be appreciated that the gassupply vessel may be of any other suitable type, in which is a fluid isheld for dispensing of gas from the vessel. Gas supply vessels of thetypes variously described in the aforementioned U.S. Pat. Nos.5,518,528; 6,101,816; 6,089,027; and 6,343,476 are presently preferredin the broad practice of the present invention, and the disclosures ofsuch patents are hereby incorporated herein by reference in theirrespective entireties.

FIG. 2 is a schematic of the flow circuitry of the reduced pressuremodule of FIG. 1, including left gas storage and dispensing vessel 50and right gas storage and dispensing vessel 52 interconnected with flowcircuitry including manifold gas flow lines 54, 56, 58, 60, 62 and 64.The flow circuitry of this arrangement has been designed for high flowof sub-atmospheric pressure gas with low internal volume and minimaldead volume. There are four types of connections to the gas manifoldflow circuitry: (i) a pump/scrubber-manifold connection; (ii) a processgas outlet-manifold connection, (iii) a purge gas-manifold connectionand (iv) a gas supply vessel-manifold connection. Each of these isdiscussed in turn below.

In the pump/scrubber-manifold connection, a vacuum source (not shown inFIG. 2) is connected to a first end of vacuum source line 60 containingautomatic flow control valve AV13 therein. Vacuum source line 60 isjoined at a second end thereof to process gas outlet line 58.

In the process gas outlet-manifold connection, a downstreamgas-consuming process unit (not shown in FIG. 2) is connected to a firstend of process gas outlet line 58, containing manual valve MV11 andautomatic valves AV15 and AV10 therein. The process gas outlet line 58also has joined thereto process gas feed line 56, containing manualvalve MV21 and automatic valves AV25 and AV20 therein.

In the purge gas-manifold connection, a source of purge gas (not shownin FIG. 2) is joined to purge gas feed line 62 at a first end thereof.The purge gas feed line 62 is joined at a second end thereof to theprocess gas outlet line 58. The purge gas feed line 62 contains afilter, pressure switch (PS1), a restricted flow orifice (RFO) andautomatic valve AV12 therein. Joined to purge gas feed line 62 is apurge gas flow line 64, containing a filter, pressure switch (PS2),restricted flow orifice (RFO) and automatic valve AV22 therein. At itsopposite end from the junction with purge gas feed line 62, the purgegas flow line 64 is joined to the process gas feed line 56.

In the gas supply vessel-manifold connection, the gas storage anddispensing vessel 50 is joined to the process gas outlet line 58,upstream of automatic valve AV10. The gas storage and dispensing vessel52 is joined to process gas feed line 56 upstream of automatic valveAV20.

In the FIG. 2 manifold arrangement, three pressure transducers arelocated on the manifold. Pressure transducer PT-11 monitors the pressureassociated with gas storage and dispensing vessel 50 and pressuretransducer PT-21 monitors the pressure associated with gas storage anddispensing vessel 52. Pressure transducer PT-31 monitors the outletpressure of the process gas as flowed to the downstream gas-consumingprocess unit, or to an extractor module interposed between the reducedpressure module and the downstream gas-consuming process unit. Thevacuum levels from the pump/scrubber are monitored by vacuum sensor VS-1in vacuum source line 60 on the portion of the manifold associated withgas storage and dispensing vessel 50, and by vacuum sensor VS-2 inprocess gas feed line 56 in the portion of the manifold associated withgas storage and dispensing vessel 52.

The source of purge gas that is joined to the purge gas feed line 62 toconstitute the purge gas-manifold connection, may be any suitable purgegas source, such as a supply tank of a purge gas such as ultra-highpurity nitrogen or ultra-high purity nitrogen/helium mixture, or othersuitable single component or multi-component gas medium, as effectivefor the purging of the flow passages of the manifold lines andassociated componentry. So-called “house nitrogen” (i.e., nitrogenavailable from the general supply utility in the semiconductormanufacturing facility) or clean dry air (CDA) from a suitable sourcethereof may be employed to actuate pneumatic automatic valves in themanifold, and to purge the main cabinet of the reduced pressure moduleas well as the associated electronics module. Gas is exhausted from themain cabinet by means of ducting coupled to the main cabinet and joinedto the exhaust system of the semiconductor manufacturing facility.

The operation of the reduced pressure module will now be described withreference to a series of screens displayed on the touch screen of theelectronics module associated with the main cabinet of the reducedpressure module.

In an initial operation, depressing the START button 28 (see FIG. 1)will begin the start up sequence of events for the system leading to theinitial MAIN MENU screen shown in FIG. 3, including touch selections for“ACCESS CODE ENTRY,” “STATUS SCREEN,” “CURRENT ALARMS,” “MAINTENANCEMENU,” “ALARM HISTORY,” “AUTO SWITCH OVER,” and “SYSTEM IDLE.”

Touch selection of “CURRENT ALARMS” from the MAIN MENU screen willgenerate a sub-menu for selection of alarm settings, e.g., silencingaudible alarms, resetting system alarms that are not active so that theyare reactivated, etc. and displaying current status of all alarms in thesystem.

After the alarms have been set as desired, a return to the MAIN MENUwill permit access code entry by touch selection of “ACCESS CODE ENTRY,”which generates a sub-menu allowing selection of the access leveldesired, including operational access, maintenance access, and totalaccess. Level selection on the access level sub-menu then generates akeypad for access code entry.

Upon return to the MAIN MENU screen (FIG. 3), touch selection of the“MAINTENANCE MENU” (discussed more fully hereinafter in connection withFIG. 6 hereof) accesses an automated gas supply vessel change routinethat can be utilized to install gas supply vessels at start-up, whichbegins with selection of the side (left-hand side or right-hand side ofthe cabinet) on which the initial gas supply vessel is to be installed.If the left-hand side gas supply vessel is to be installed, thecorresponding selection on the touch screen will generate the “LEFTCYLINDER MENU” shown in FIG. 4. The “RIGHT CYLINDER MENU” is of a sameformat.

The “LEFT CYLINDER MENU” as shown in FIG. 4 includes touch selectionsfor “TOOL EVACUATION,” “GAS ON,” “TOOL PURGE,” “LOCAL EVACUATION,” “TOOLPUMP PURGE,” “LOCAL PUMP PURGE,” “CYLINDER CHANGE,” and “MAIN MENU.”

Pressing the “CYLINDER CHANGE” button on the touch screen will actuatethe gas supply vessel change routine and generate the screen displayshown in FIG. 5 with a prompt, “Replace Cylinder,” denoting that theleft-hand gas supply vessel can be installed in the main cabinet. Aftera filled gas supply vessel has been installed in the left bay of themain cabinet of the reduced pressure module, touch selection of“Continue” at the lower left-hand portion of the screen will cause thesystem to complete the cylinder change routine, and deploy the installedgas supply vessel for gas dispensing operation. The process then can berepeated in corresponding fashion for the right-hand gas supply vesselinstallation.

The reduced pressure module allows delivery and control ofsub-atmospheric pressure gas from two gas supply vessels to a singleoutlet connection, in the embodiment shown in FIG. 1. The system isconstructed and arranged to control automatic switchover from thestarting gas supply vessel to the back-up gas supply vessel upondepletion of the starting gas supply vessel. After replacing thedepleted cylinder, the system can be reset to autoswitch back to theoriginal starting side.

As discussed hereinabove, the control system has two operationalsub-menus, “LEFT CYLINDER” and “RIGHT CYLINDER” for the respectiveleft-hand and right-hand gas supply vessels. These sub-menus areaccessed through the MAIN MENU of the touch screen by pressing theMAINTENANCE MENU button to generate the screen shown in FIG. 6, whichincludes touch selections for “L/C MAINTENANCE MENU,” “R/C MAINTENANCEMENU,” “ANALOG CALIBRATION,” “MANUAL CONTROL,” “CURRENT ALARMS,”“OPERATING PARAMETERS” and “MAIN MENU,” wherein “L/C” means LeftCylinder and “R/C” means Right Cylinder. Selection of “MANUAL CONTROL”or “I/C MAINTENANCE MENU” or “R/C MAINTENANCE MENU” then permits “GASON” and maintenance operations to be selected (see FIG. 4).

The reduced pressure module in an illustrative embodiment has six (6)basic modes of operation, comprising:

-   1. All Valves Closed: at start-up, following a fatal alarm or power    down/power failure, gas off on both cylinders.-   2. Gas On Left Cylinder—Auto Switchover Off: runs to depletion of    the Left cylinder, sends “Cylinder Empty” signal.-   3. Gas On Right Cylinder—Auto Switchover Off: runs to depletion of    the Right cylinder, sends “Cylinder Empty” signal.-   4. Gas On Left Cylinder—Auto Switchover On: runs to depletion of the    Left cylinder, switches to the Right cylinder.-   5. Gas On Right Cylinder—Auto Switchover On: runs to the depletion    of the Right cylinder, switches to the Left cylinder.-   6. Manual Operation: manual selection of all valves except the    cylinder valves.

The reduced pressure module can be fitted with manual gas supply vesselvalves or with pneumatic gas supply vessel valves, with the selection ofvalve type being made in the parameter set-up operation.

The “STATUS SCREEN” is shown in FIG. 7 and is accessed by correspondingtouch screen selection on the “MAIN MENU.” The “STATUS SCREEN” displaysthe status of all valves in the reduced pressure module, e.g., by asuitable color scheme (red coloration of the corresponding valvesdenoting closed valves, and green coloration of corresponding valvesdenoting open valves), or other visually perceptible differentiation.The “STATUS SCREEN” also displays the “GAS ON” or “GAS OFF” state ofeach gas supply vessel in the reduced pressure module, the pressurereading, e.g., in units of torr, of each pressure transducer in thereduced pressure module, and the temperature of each of the gas supplyvessels. Gas flow in the reduced pressure module may be turned off fromthe “STATUS SCREEN.”

The system is arranged so that a local evacuation must be run at thespecific one of the left or right sides of the manifold flow circuitryat which gas is to be dispensed in a “GAS ON” mode. This localevacuation function is actuated by touch selection of the “LOCALEVACUATION” button on the appropriate (left or right) gas supply vesselmenu (“LEFT CYLINDER MENU” or “RIGHT CYLINDER MENU”). The “AUTO SWITCHOVER” button on the “MAIN MENU” is accessed and the autoswitch functionis inactivated before the local evacuation and gas flow steps areinitiated.

Subsequent to local evacuation, the “GAS ON” button is touch selected onthe appropriate (left or right) gas supply vessel menu (“LEFT CYLINDERMENU” or “RIGHT CYLINDER MENU”). This action generates the screen shownin FIG. 8 for the left-hand gas supply vessel, if the left-hand vesselis selected, or a corresponding screen for the right-hand gas supplyvessel, if the right-hand vessel is selected, and opens the gas supplyvessel valve (AV-10 or AV-20) if “Pneumatic Cylinder Valve” is selected,or a prompt the user to open the manual gas supply vessel valve if“Manual Cylinder Valve” is selected (screens not shown). The pigtailvalve (AV-11 or AV-21) and tool isolation valve (AV-15 or AV-25) willalso be opened, charging the manifold and delivery line withsub-atmospheric gas.

To set up the system for Auto Switchover, the “AUTO SWITCH OVER” screenis accessed on the “MAIN MENU” and an “AUTO SWITCHOVER” button (screennot shown) is pressed, following which the operator exits the screen,and returns to the “GAS ON” screen button for the gas supply vessel thatis opposite the one previously turned on, i.e., the “GAS ON” button onthe “RIGHT CYLINDER MENU” is selected if the left-hand gas supply vesselis the one that was previously active in the dispensing mode, and viceversa. By pressing the “GAS ON” button for such previously inactive gassupply vessel, the gas supply vessel valve (AV-10 or AV-20) will open aswell as the pigtail valve (AV-11 or AV-21). The “stick” isolation valve(AV-15 or AV-25) will not open until the Auto Switchover point has beenreached.

The “GAS OFF” condition can be controlled by either the “STATUS SCREEN”in the “MAIN MENU” or in the “GAS ON” screen of the appropriate “LEFTCYLINDER MENU” or “RIGHT CYLINDER MENU.” Pressing the “GAS OFF” buttonwill close all valves on the gas supply vessel side that is selected(valves AV-10, AV-11, and AV-15 on the left side, and valves AV-20,AV-21 and AV-25 on the right side), stopping the flow of gas from thegas supply vessel to the manifold and from the manifold to the tooldelivery line. By pressing the Left or Right cylinder icons, theoperator can toggle back and forth between the respective gas supplyvessels. If the “Auto Switchover” setting were active, then turning thecurrent “GAS ON” cylinder to “GAS OFF” will initiate an Auto Switchover.This is prevented from occurring by turning off the standby gas supplyvessel first, and then turning off the active gas supply vessel.Following “GAS OFF” establishment, the manifold lines will still becharged with sub-atmospheric pressure gas until purged or evacuated.

The “CURRENT ALARMS” screen on the electronics module can be actuated todisplay all active alarms, and afford the operator the opportunity toreset alarm conditions, or to suppress one or more types of alarm, andto view the alarm history of the system, by frequency and by occurrence.The alarms may for example be actuated for the following alarmconditions: cabinet ventilation failure; door interlock alarm; toxic gasdetection; insufficiency of vacuum/pressure; vacuum differential; andillegal analog input. The electronics module can also have monitoringdevices, e.g., sensors and detectors, coupled to it, and operativelyassociated with the alarms, so that an alarm is actuated for example ifa toxic gas monitor senses the presence of a gas species that ishazardous in character, and valves are actuated to close (e.g., AV-15 orAV-25) and to subsequently reopen when the alarm-triggering condition isterminated or resolved.

Pressing the “MAINTENANCE MENU” button on the “MAIN MENU” elicits thescreen shown in FIG. 6, allowing the operator to select the left side orthe right side maintenance operations, by touch selection of thealternative “L/C MAINTENANCE MENU” and “R/C MAINTENANCE MENU” buttons,which in turn accesses the respective “TOOL EVACUATION,” “TOOL PURGE,”“TOOL PUMP PURGE,” “LOCAL EVACUATION,” “LOCAL PUMP PURGE,” “CYLINDERCHANGE” and “GAS ON” buttons on the maintenance menu for the respectiveside (and gas supply vessel) of the main cabinet.

If the “CYLINDER CHANGE” button is pressed, the first cylinder changescreen shown in FIG. 9 is accessed, which is the screen for thePreChange Leak Test. The PreChange Leak Test screen shows a schematicdepiction of the gas panel, including valve states and pressuretransducer pressure level. At the bottom of the PreChange Leak Testscreen is a display of the elapsed time and the total time of the LeakTest.

The program next prompts the operator to turn the gas supply vessellock-out switch to “off” and to lock the automatic gas supply vesselvalve in the closed position and then to press “Enter.” Once “Enter” hasbeen pressed the purge inlet pressure is checked at pressure sensorPS-01. If there is sufficient pressure, automatic valve AV-12 is openedand the pressure is verified at pressure transducer PT-11. If the purgepressure is determined to be insufficient during these two steps, thenthe system will alarm and wait for operator input. Automatic valve AV-11will open to pressurize the “stick” (portion of the manifold associatedwith a given vessel) up to the gas supply vessel valve. After a shortdelay, automatic valve AV-12 closes, the pressure value is captured andthe pressure leak-down test timer starts. If the leak-down rate is lessthan the value in the set-up table, the leak test will concludesuccessfully. Upon successful completion of the leak test, the LocalPurge Cycle screen will appear.

The second cylinder change screen is the Local Purge Cycle screen, andis shown in FIG. 10. To start the local purge cycle, automatic valveAV-15 opens, and the vacuum level is checked at vacuum sensor VS-01.Once the vacuum sensor is satisfied and responsively closes, the ventisolation valve AV-13 is opened and the vacuum level at pressuretransducer PT-11 is compared to the value in the set-up parameters ofthe system. When the sensed pressure of the pressure transducer PT-11 isbelow the pre-programmed vacuum level, the vent valve, AV-13, is closedand the purge valve, AV-12, is opened, thereby pressurizing the gasstick to the preset purge gas pressure. The above sequence is repeatedfor the number of cycles established in the set-up routine in the systemprogram. After completing the cycles, the next screen in the CylinderChange procedure is displayed.

The third of the cylinder change screens is shown in FIG. 11, andinstructs the operator to replace the cylinder. Upon breaking the CGAfitting associated with the gas supply vessel being changed out, anitrogen purge will flow out of the open pigtail portion of the manifoldto prevent backflow of air into the pigtail. When the new gas supplyvessel has been installed and the CGA fitting tightened to theappropriate torque, the Continue button is pressed, thereby generatingthe screen shown in FIG. 12.

The screen shown in FIG. 12 is a Post Cylinder Change Leak Test screen.The post cylinder change leak test is a rate of rise or “leak-up” test.The system is evacuated by the Local Evacuation procedure, using vacuumfrom the Pump/Scrubber, and then sealed and the pressure monitored forany upward change indicating a leak. As soon as the protocol is entered,automatic valve AV-15 opens and after a short delay, automatic valveAV-13 opens to evacuate the system. The vacuum level is measured bypressure transducer PT-11. After a brief stabilization delay, automaticvalve AV-13 closes and the vacuum level is captured. At this point, thetimer starts and runs for the time determined by the system set-upprogram. If the vacuum has not changed more than the set-up programallows, the system has passed the post change leak test.

When time for the leak test has expired, and the leak test timer hasreached zero, the Post Change Purge screen appears, as shown in FIG. 13.The post-change cycle purge operation then commences its automated purgeand evacuation routines. During the post-change purge, the cyclesetpoint and current cycle count are displayed. Once the system hascompleted the preset number of evacuation and purge cycles according tothe program, a screen will appear informing the operator that thecylinder change routine has been completed, whereupon the Enter buttoncan be selected by the operator to return to the Main Menu.

In order to carry out the tool evacuation operation, the appropriate gassupply vessel “CYLINDER MENU” is accessed, and the “TOOL EVACUATION”button is selected. This generates the screen shown in FIG. 14, andopens the tool isolation valve (AV-15 or AV-25) and evacuates the gaspanel up to the cylinder valve (AV-10 or AV-20) using the vacuum systemof the tool. If the tool vacuum is insufficient (less than the setpointestablished in the set-up parameters), the tool isolation valve (AV-15or AV-25) will not open and an alarm will activate. The “TOOLEVACUATION” operation remains in effect until terminated by the operatorby pressing the “STOP” button at the lower right-hand portion of thescreen.

The “TOOL PURGE” menu next is selected from the appropriate gas supplyvessel “CYLINDER MENU” to generate the screen shown in FIG. 15. The“TOOL PURGE” then commences, providing an inert gas purge from the purgeinlet to the process tool by opening automatic valve AV-12 or AV-22, andby opening automatic valve AV-15 or AV-25. The minimum tool purgepressure set point (as established on the general setup screen, accessedby the screen sequence “MAIN MENU” → “MAINTENANCE MENU” → “OPERATINGPARAMETERS”) must be maintained at pressure transducer PT-31 for thepurge to continue. The tool purge remains in effect until the operatorpresses the Stop button.

Next, the tool pump purge operation is carried out, by selecting the“TOOL PUMP PURGE” menu from the appropriate gas supply vessel “CYLINDERMENU” to generate the screen shown in FIG. 16 and initiate theoperation, during which the stick of the manifold is alternatelyevacuated and then pressurized with purge gas. Automatic valve AV-15 orAV-25 opens to evacuate the gas stick up to the cylinder valve, AV-10 orAV-20, using the vacuum system of the tool. The automatic valve AV-15 orAV-25 will not open unless the tool vacuum at pressure transducer PT-31is below the minimum tool vacuum setpoint. Once the pressure at pressuretransducer PT-11 or PT-21 is below the minimum vacuum level setpoint, atimer begins counting. When the timer counts out, automatic valve AV-015or AV-25 closes, and automatic valve AV-12 or AV-22 opens to fill themanifold with purge gas. When the pressure at pressure transducer PT-11or PT-21 is greater than the minimum purge setpoint, another timerbegins counting and the system continues to purge until the timerreaches the number of cycles in the set-up. This two-part cycle isrepeated for the programmed number of cycles and automatically ends byleaving the gas panel under vacuum.

The local evacuation operation then is carried out, by selecting the“LOCAL EVACUATION” menu from the appropriate gas supply vessel “CYLINDERMENU” to generate the screen shown in FIG. 17 and initiate theoperation, to evacuate the gas stick using the vacuum supplied from thePump/Scrubber. The presence of vacuum is verified at vacuum sensor VS-01or VS-02, and automatic valve AV-13 or AV-23 is opened and the vacuumlevel is checked at pressure transducer PT-11 or PT-21. Once the vacuumlevel at PT-11 or PT-21 is below the minimum vacuum setpoint, automaticvalve AV-11 or AV-21 is opened to evacuate the stick up to the cylindervalve. The local evacuation remains in effect until the operator pressesthe Stop button. During this operation, the gas cabinet is isolated fromthe tool and delivery line by closing the manual tool isolation valve.

Next, the local pump purge operation is carried out, by selecting the“LOCAL PUMP PURGE” menu from the appropriate gas supply vessel “CYLINDERMENU” to generate the screen shown in FIG. 18 and initiate theoperation, which begins by performing a “LOCAL EVACUATION” function asdescribed hereinabove. When the vacuum level at pressure transducerPT-11 or PT-21 is below the minimum vacuum setpoint, the evacuationtimer begins counting. When the timer counts out, automatic valve AV-13or AV-23 closes, pressure sensor PS-01 checks that there is sufficientpurge pressure, and automatic valve AV-12 or AV-22 opens to deliverpurge gas to the stick. When the pressure at pressure transducer PT-11or PT-21 is greater than the minimum purge pressure setpoint, the purgetimer begins counting. When this timer counts out, the purge gasautomatic valve AV-12 or AV-22 is closed and the venturi isolation valveAV-13 or AV-23 opens to evacuate the stick back to the cylinder valve.This sequence is repeated for the programmed number of cycles,automatically ending with evacuation of the manifold. During thissequence, the tool is isolated from the gas cabinet by closing themanual stick isolation valve.

The reduced pressure module can be operated in a manual mode byaccessing the “MAINTENANCE MENU” and selecting “MANUAL CONTROL.” In thismode, a screen is generated that depicts the gas panel, showing thevalve states and the pressure readings for all transducers, and valveicons on the screen can be toggled to open or close the correspondingvalves of the manifold.

Operating parameters can be established in the set up of the system bythe screen sequence “MAIN MENU” → “MAINTENANCE MENU” → “OPERATINGPARAMETERS,” as described hereinabove. The operating parameters that aresettable (with units denoted in parentheses) include the following:

General Setup

-   -   Cylinder Low (Torr): point at which the system will warn the        user that the cylinder is approaching empty and a replacement        should be ordered.    -   Cylinder Change-Over (Torr): point at which the system will warn        the user that the cylinder is empty and switch to the back-up        cylinder (if Auto Switchover is active).    -   Minimum Tool Vacuum (Torr): The minimum vacuum that the system        must detect from the tool.    -   Balance Delay (Secs): the delay time to allow transducer reading        stabilization.    -   Vacuum Delta P (Torr): allowable reverse reading between        transducers under vacuum.    -   Cylinder Valve: select the type of valve on the cylinders being        installed.        Tool Evacuate    -   Minimum Tool Vacuum (Torr): the minimum vacuum that must be seen        at pressure transducer PT-31 before valves will open in the tool        evacuate and tool pump purge protocol.        Local Evacuate    -   Minimum Vacuum Set Point (Torr): the minimum vacuum that must be        seen at pressure transducer PT-11 or PT21 to allow Local        Evacuate to continue.        Tool Pump Purge    -   Vacuum Cycle Delay (Secs): time delay to allow the vacuum to        stabilize.    -   Minimum Purge Pressure (Torr): pressure that must be attained        during the purge pressurization.    -   Pressure Cycle Delay (secs): time delay to allow the pressure to        stabilize.    -   Minimum Tool Vacuum (Torr): The minimum vacuum that must be seen        at pressure transducer PT-31 before valves will open during a        tool pump purge.    -   Number of Purge Cycles: number of pressure/vacuum cycles.        Local Pump Purge    -   Minimum Vacuum Set Point (Torr): the minimum vacuum that must be        attained by the vacuum source.    -   Vacuum Cycle Delay (secs): time delay to allow the vacuum to        stabilize.    -   Minimum Purge Pressure at Pressure Transducer PT-11 or PT21        (Torr): purge gas pressure that must be attained.    -   Pressure Cycle Delay (Secs): time delay to allow the pressure to        stabilize.    -   Number of Purge Cycles: number of pressure/vacuum cycles.        Cylinder Change    -   Minimum Leak Test Pressure (Torr): the minimum pressure that        must be attained during the leak-down test.    -   Decay in Pressure Allowed (Torr): the loss of pressure that is        allowed during the leak-down test.    -   Pre-change Leak Test Time (Min): This is the leak test time at        the beginning of a cylinder change to verify that the cylinder        valve has been sealed properly.    -   Pressure Transducer PT11/PT21 Minimum Pressure (Torr): the        minimum pressure that must be attained during the cylinder        change while the pigtail is disconnected.    -   Minimum Leak Test Vacuum (Torr): the vacuum that must be        attained to carry out the leak-up test.    -   Rise in Pressure Allowed (Torr): This is the acceptable pressure        rise allowed during the leak-up test.    -   Post-Change Leak Test Time (min): This is the leak test time for        the leak-up test after a new cylinder has been connected to        verify that the CGA fitting has been tightened properly.    -   Manifold Pressure Delay (Secs): pressure stabilization time        before alarm.

The Pump/Scrubber connected with the reduced pressure module is adaptedto provide the motive capability for effecting flow of gas through themanifold of the reduced pressure module, via the Pump component, and totransport the gas to the downstream tool or other gas-consuming processunit, or alternatively to flow the gas to the Scrubber component of thefacility.

The Pump component can be of any suitable type, including a suitabledevice selected from among pumps, blowers, fans, compressors, ejectors,eductors, etc., as appropriate to the delivery and processing of gas inthe facility in which the reduced pressure module and associated Pumpcomponent is employed. The Scrubber likewise can be of any suitabletype, including wet scrubbers, dry scrubbers, mechanical scrubbers,oxidation scrubbers, etc.

The Pump component can also be a constituent of an extractor module 100as shown in FIG. 19, which may comprise a pump and a surge tank (notshown in FIG. 19; see FIG. 20, described more fully hereinafter), alongwith controls and safety systems appropriate for safe operation. Theextractor system components may be housed in an exhausted and monitoredenclosure, with the gas delivery hardware being housed in a main cabinet102 equipped with viewing window 108, and with associated controlelectronics being located in a separate enclosure 104 mounted on the topof the main cabinet 102, in a manner generally analogous to the hardwareand electronics arrangement of the reduced pressure monitor as describedhereinabove.

The extractor system extracts the gas from the reduced pressure moduleand boosts the pressure to a constant level for downstream gas-consumingtools operating at mild vacuum pressure, with the pumping systemoperating automatically to maintain a constant sub-atmospheric pressurein the surge tank regardless of flow rate of gas. Evacuation and purgingof the extractor system are done manually, since no routine shut-down isrequired (as in a gas cabinet in which gas cylinders must be changedperiodically).

A programmable logic controller (PLC) and companion color touch screen106 provide preprogrammed functionality and local indication of valvestatus and system pressures. Surge tank pressure control is achievedthrough control of the pump speed.

The main cabinet 102 thus constitutes a pumper cabinet that encloses asurge tank 120 and an extractor pump 122, as shown in FIG. 20, processplumbing and the purge and vent plumbing and is monitored for exhaustpressure. The surge tank can be of any suitable volume, e.g., from about25 liters to about 150 liters, as appropriate to the specific gasdelivery operation involved. The window 108 in the upper door of themain cabinet 102 is a fire-rated safety glass window to allow visualinspection of the condition of the manifold prior to opening the door.The doors are suitably secured with manual twist latches. The colortouch screen interface 106, EMO (Emergency Machine Off) button and theSTART button are located on the front of the electrical enclosure 104 ontop of the main cabinet 102.

The pump speed control of pump 122 is accommodated by a proportionalintegral derivative (PID) control loop in the programmable logiccontroller (PLC) of the extractor module. The PLC compares the surgetank pressure in surge tank 120 to a set point, and generates a voltageoutput that is fed to a variable frequency drive (VFD), which in turncontrols the speed of the pump motor by varying the frequency fed to thethree-phase motor. As the flow requirement increases or as the inletpressure decreases, the pump speed will increase proportionally tomaintain a constant pressure in the surge tank.

FIG. 21 shows an illustrative Status Screen for the extractor module.The Status Screen displays the status of all valves, which as in thereduced pressure module may be color-coded or otherwise visuallyperceptible as to state (e.g., being displayed in red for closed and ingreen for open), the pressure reading of each pressure transducer, thetemperature in the surge tank, the state of the pressure switches, andthe status of the pump (ON or OFF).

FIG. 21 thus shows the flow circuitry of the manifold in the extractormodule, and the components of the module, as including a leak test portF1 (“Leak Check Port”) which is closed off by manual valve MV-2. Threepressure transducers are located on the manifold: PT-1 monitors thepressure at the system inlet; PT-2 monitors the pump outlet pressure;PT-3 monitors the surge tank pressure, which is also the outlet pressureto the downstream process tool. During the purging of the manifold, theincoming purge gas pressure is monitored by pressure switch PS1. Thevacuum level (from a Pump/Scrubber or other vacuum source) is monitoredby vacuum sensor VS-1. The gas temperature at the inlet to the surgetank is monitored by thermocouple TS-1. If either of the pressure reliefvalves PRV-1 or PRV-2 should open, flow detector FS-1 will direct flowto the scrubber.

The extractor module employs a “MAIN MENU” in an analogous fashion tothe reduced pressure module, with the “MAIN MENU” displaying touchselections including “ACCESS MENU,” “ALARMS,” “ALARM HISTORY,” “SYSTEMSTATUS,” “PUMP CONTROL,” “UNIVERSAL MENU” and “SYSTEM IDLE.”

To start the pump, the operator selects “PUMP CONTROL” from the “MAINMENU” to generate the screen shown in FIG. 22, and the “Pump Run”selection is made on the screen. If the pressure in the surge tank isbelow the set point (e.g., ˜600 Torr), the pump will turn on to bringthe pressure up to the set point. A screen display will then appear,directing the operator to open the manual valve (not shown in FIG. 22,but which is disposed in the “TO VMB” (Valve Manifold Box) line shown atthe right-hand portion of the drawing), in order to open the flow pathof the system to the downstream process tool. After the operatorconfirms that the manual valve is open, and that the gas deliveryoperation should commence, the pneumatic outlet block valve AV-4 isopened by the system to effect gas flow to the tool. To turn off thepump, the “Pump Stop” selection is made on the Pump Control screen shownin FIG. 22. The system will then stop the pump and isolate the system byclosing valves AV-1 and AV4.

The extractor module is also selectively actuatable to carry outevacuation and purging operations, involving valves MV-3, AV-1, AV-2,AV-3, AV-4 and AV-7. A manual mode of operation is also accommodated bythe system.

Operating parameters can be established in the set up of the extractormodule by the screen sequence “MAIN MENU” → “MAINTENANCE MENU” →“OPERATING PARAMETERS.” The operating parameters that are settable (withunits denoted in parentheses) include the following:

Operating Parameters

-   -   PT-1 Set Point (Torr): pressure above which the system will not        allow the inlet block valve AV-1 to open.    -   PT-2 Set Point (Torr): pressure at which the system will warn        the user that the system is above atmospheric pressure.    -   PT-3 Set Point (Torr): pressure above which the system will shut        off the pump.    -   PT-2/3 Delta (Torr): looks at the pressure drop across the        particle filter to determine if the filter is becoming plugged.

FIG. 23 is a schematic block diagram of an integrated semiconductormanufacturing facility 200 showing the reduced pressure module (RPM) 202joined in gas flow communication with an extractor module (EXTRACTOR)204 which in turn is coupled in gas flow communication with asemiconductor manufacturing gas-consuming unit (TOOL) 206, with each ofRPM 202, EXTRACTOR 204, and TOOL 206 being joined in exhaustrelationship with scrubber unit (SCRUBBER) 208 for abatement of thetoxic/hazardous gas species in the gas flowed to the SCRUBBER from theRPM, EXTRACTOR and/or TOOL, and final discharge of the treated effluentfrom the scrubber in discharge line 210.

In accordance with the present invention, the addition of a time delayto the auto-switchover action in the reduced pressure module allows theextractor cabinet to be warned in advance of the auto-switchover takingplace. The extractor cabinet then can take action to prevent theintroduction of a pressure spike to the inlet of the fast runningextractor pump. The reduced pressure module and extractor module areprogrammatically arranged in their respective electronics modules, tocarry out the sequence of steps identified in FIGS. 24A and 24B.

The time delay auto-switchover sequence of the invention is initiatedwhen the gas supply vessel that is actively dispensing gas for flow tothe downstream extractor module reaches its empty or endpoint limit.Such limit, marking the end of the useful dispensing operation of theon-stream gas supply vessel, may be demarcated by any suitable meansand/or method. For example, the empty/endpoint limit may be demarcatedby a specific weight of the vessel approaching its tare weight,indicating that the contained gas is depleted to a desired degree forchange-over to a fresh gas supply vessel. As another alternative, theempty/endpoint limit may be a set point determined by a cumulative timeof dispensing operation. As yet another alternative, the empty/endpointlimit may be determined by a diminution of pressure and/or flowrate ofthe dispensed gas, to a level indicative that the gas supply vessel isapproaching or at empty status. Any other approaches, e.g., rate ofchange of one or more characteristics of the dispensed gas, may beemployed to establish or detect an end-stage limit to the gas dispensingoperation involving the on-stream gas supply vessel.

Regardless of how determined, the empty/endpoint limit when reached issensed (Step 1 in FIG. 24A), e.g., by a weight sensor, pressuretransducer, flowrate sensor, volumetric (cumulative) flowmeter, cycletimer, etc., as appropriate to the specific mode of determination of thelimit point, and a limit sensing signal is generated in the electronicscircuitry of the reduced pressure module, which is programmably arrangedwith the electronics circuitry of the extractor module to effect thetime delay auto-switchover sequence. The limit-sensing signal then istransmitted in the electronics enclosure of the reduced pressure moduleto a closable contact, relay or other actuatable means, to induceswitching of such means to a switched condition indicative of the limitsensing. For example, in the sequence illustrated in FIG. 24A, thecontact is closed (Step 2).

The extractor module then senses the contact closure in the reducedpressure module as an input (Step 3 in FIG. 24A). Such input may beeffected by a current signal transmitted from circuitry including theclosed contact in the reduced pressure module to the control circuitryin the electronics compartment of the extractor module. The controlcircuitry in the electronics compartment of the extractor module thenresponsively operate to close the pump inlet valve (valve AV-3 as shownin FIGS. 21 and 22) for a time interval that is denoted in FIG. 24A astime T2 (Step 4). Concurrently, the extractor module control circuitrystalls the pump, e.g., by switching off the power to the variablefrequency drive (VFD) for such pump, for a time interval that is denotedin FIG. 24A as time T3 (Step 5).

The closing of the closable contact in the reduced pressure module alsoactuates a timer in the electronics circuitry of such module. The timeris actuated to count down a time delay interval denoted in FIG. 24A astime T1, until the time delay interval T1 has been reached (Step 6). Atthis point, auto-switchover of the gas supply vessels in the reducedpressure module takes place (Step 7), to switch the flow of dispensedgas from the exhausted gas supply vessel to a fresh (gas-filled) gassupply vessel, to ensure continuity of gas dispensing operation.

Gas then is flowed from the fresh gas supply vessel in the reducedpressure module to the extractor module (Step 8) and such flow continuesuntil the pump inlet valve closure time interval T2 has been reached,which may be determined by a time that is actuated in the electronicscircuitry of the extractor module at the beginning of Step 4. When thepump inlet valve closure time interval T2 has been reached (Step 9), thepump inlet valve (AV-3 as shown in FIGS. 21 and 22) opens to introducegas to the pump inlet (Step 10). Such actuation of the pump inlet valvemay be effected by operatively coupling the timer with a pneumaticactuator for the pump inlet valve, so that the timer on reaching timeinterval T2 actuates a switch to initiate gas flow to the pneumaticactuator for the pump inlet valve.

Gas then continues to flow from the reduced pressure module to the pumpin the extractor module, until the pump inactivation time interval T3 isreached (Step 11). At this point, the pump is actuated to resumerunning. The pump inactivation time interval T3 may be dynamicallyprogrammably established by a proportional integrating derivative (PID)control loop in the electronics circuitry of the extractor module whichis operatively coupled with pressure transducers in the extractormodule, so that the resumption of pump operation is “smoothed” inrelation to pressures in the manifold gas flow circuitry of theextractor module to minimize pressure and flow rate perturbations in theflow circuitry and to eliminate the pressure spikes that arecharacteristic of operation of the prior art system in the absence ofthe time delay auto-switchover sequence of the invention. The PIDcontrol loop for such purpose may be operatively coupled with thevariable frequency drive (VFD) of the pump, to energize the VFD inreinitiation of the pump operation. Alternatively, the time interval T3can be set by a timer in the auto-switchover system.

The foregoing time delay auto-switchover sequence of the invention hasbeen illustratively described above in reference to a reduced pressuremodule in combination with an extractor module. It will be recognized,however, that the invention is not thus limited, but rather may bepracticed with any multiple vessel array in which a downstream pump orother motive fluid driver is susceptible to pressure spikes at the pumpoutlet in response to substantial pressure variation at the pump inletincident to switchover of gas supply from one vessel to another in themultiple vessel array. Further, although the invention has beenillustratively described in reference to a two-vessel array, it will berecognized that the invention is amenable to implementation in multiplevessel arrays including more than two gas supply vessels. Finally, whilethe invention has been described with reference to specific circuitryand control elements and relationships herein, it will be recognizedthat the general methodology of the invention as illustratively set outand described with reference to FIGS. 24A and 24B hereof can beimplemented in any of numerous hardware/software configurations andformats.

It will be appreciated that the apparatus and method of the inventionmay be practiced in a widely variant manner, consistent with the broaddisclosure herein. Accordingly, while the invention has been describedherein with reference to specific features, aspects, and embodiments, itwill be recognized that the invention is not thus limited, but issusceptible of implementation in other variations, modifications andembodiments. Accordingly, the invention is intended to be broadlyconstrued to encompass all such other variations, modifications andembodiments, as being within the scope of the invention hereinafterclaimed.

1. A gas supply and dispensing system, comprising: an array of at leasttwo gas storage and dispensing vessels arranged for sequential on-streamdispensing operation involving switchover from a first vessel to asecond vessel in the array; a pump coupled in gas flow communicationwith the array for pumping of gas derived from an on-stream one of thevessels in the array, and discharge of pumped gas in the dispensingoperation; an auto-switchover system constructed and arranged to sensean endpoint limit of the on-stream one of the vessels and to initiateauto-switching from the on-stream one of the vessels to another of thevessels in the array having gas therein, for subsequent dispensing ofgas from said another of the vessels, as a subsequent on-stream vesselin the dispensing operation; wherein the auto-switchover system betweensensing of the endpoint limit and initiating auto-switching terminatesflow of gas to the pump and inactivates the pump; and wherein theauto-switchover system after initiating auto-switching reinitiates flowof gas to the pump and reactivates the pump.
 2. The system of claim 1,wherein the endpoint limit is sensed by the auto-switchover system as anendpoint limit weight of the on-stream one of the vessels.
 3. The systemof claim 1, wherein the endpoint limit is sensed by the auto-switchoversystem as an endpoint limit pressure of gas dispensed from the on-streamone of the vessels.
 4. The system of claim 1, wherein the endpoint limitis sensed by the auto-switchover system as an endpoint limit flow rateof gas dispensed from the on-stream one of the vessels.
 5. The system ofclaim 1, wherein the endpoint limit is sensed by the auto-switchoversystem as an endpoint limit cumulative volume of gas dispensed from theon-stream one of the vessels.
 6. The system of claim 1, wherein theendpoint limit is sensed by the auto-switchover system as an endpointlimit rate of change of a characteristic of gas dispensed from theon-stream one of the vessels.
 7. The system of claim 1, wherein theendpoint limit is sensed by the auto-switchover system as an endpointlimit dispensing time of gas dispensing from the on-stream one of thevessels.
 8. The system of claim 1, wherein the auto-switchover systemcomprises a timer for controllably setting a time interval during whichflow of gas to the pump is terminated.
 9. The system of claim 1, whereinthe auto-switchover system comprises a timer for dynamically setting atime interval during which flow of gas to the pump is terminated. 10.The system of claim 9, wherein said timer comprises a proportionalintegrating derivative (PID) control loop.
 11. The system of claim 10,wherein said proportional integrating derivative (PID) control loop thatis operatively coupled with a pressure transducer in flow circuitrycoupling the pump in gas flow communication with the array of gasstorage and dispensing vessels.
 12. The system of claim 1, wherein theauto-switchover system comprises a timer.
 13. The system of claim 1,wherein the auto-switchover system comprises a timer for controllablysetting a time interval during which the pump is inactivated.
 14. Thesystem of claim 1, wherein the auto-switchover system is constructed andarranged to terminate flow of gas to the pump prior to inactivating thepump.
 15. The system of claim 1, wherein the auto-switchover system isconstructed and arranged to reinitiate flow of gas to the pump prior toreactivating the pump.
 16. The system of claim 1, wherein the gasstorage and dispensing vessels hold a solid-phase physical adsorbenthaving sorptive affinity for gas stored in and dispensed from thevessels.
 17. The system of claim 16, wherein the solid-phase physicaladsorbent comprises a material selected from the group consisting ofmolecular sieves, carbon, silica, alumina, clays and macroreticulatepolymers.
 18. The system of claim 16, wherein the solid-phase physicaladsorbent comprises carbon.
 19. The system of claim 1, wherein said gascomprises a semiconductor manufacturing gas.
 20. The system of claim 1,wherein the gas storage and dispensing vessels comprise interiorlydisposed regulators.
 21. The system of claim 1, wherein the gas storageand dispensing vessels are disposed in a gas cabinet.
 22. The system ofclaim 21, wherein the gas storage and dispensing vessels are coupled ingas flow communication to a valved manifold in the gas cabinet.
 23. Thesystem of claim 22, wherein the pump is contained in a pumper cabinet.24. The system of claim 23, wherein the pumper cabinet further containsa surge tank in pumped gas-receiving relationship to the pump.
 25. Thesystem of claim 24, wherein the pump and surge tank are coupled in gasflow communication with a valved manifold in the pumper cabinet.
 26. Thesystem of claim 25, wherein the valved manifold in the gas cabinet iscoupled in gas flow communication with the valved manifold in the pumpercabinet.
 27. The system of claim 26, constructed and arranged to carryout an auto-switchover operational sequence including: sensing a vesselempty endpoint limit; generating a corresponding limit sensing signal;switching a switchable actuator in response to said limit sensing signalto a switched condition indicative of the limit sensing, and actuating atimer for counting down a predetermined time interval T1; in response tothe switched condition of the switchable actuator, terminating flow ofgas to the pump for a predetermined time interval T2; stalling the pumpfor a predetermined time interval T3; after expiration of the timeinterval T1, switching gas dispensing flow, from a first vessel forwhich the vessel empty endpoint limit has been sensed, to a second,fresh vessel; dispensing gas from the second, fresh vessel, and at theexpiration of the time interval T2, flowing gas from the second, freshvessel to the pump; at the expiration of the time interval T3,reactuating the pump.
 28. The system of claim 1, wherein gas flowtermination to the pump, inactivation of the pump, reinitiation of gasflow to the pump and reactivation of the pump by the auto-switchoversystem substantially reduces pressure variation of pumped gas dischargedfrom the pump, in relation to a corresponding gas supply and dispensingsystem wherein the auto-switchover system is not constructed andarranged for gas flow termination to the pump, inactivation of the pump,reinitiation of gas flow to the pump and reactivation of the pump inconnection with the switchover from said first vessel to said secondvessel in the array.
 29. The system of claim 28, wherein the pumped gasdischarged from the pump during the switchover from said first vessel tosaid second vessel in the array is characterized by an absence ofpressure spike behavior in the pumped gas.
 30. A method of substantiallyreducing pressure variation of pumped gas discharged from a pump in agas supply and dispensing system comprising an array of at least two gasstorage and dispensing vessels arranged for sequential on-streamdispensing operation involving switchover from a first vessel to asecond vessel in the array, wherein the pump is coupled in gas flowcommunication with the array for pumping of gas derived from anon-stream one of the vessels in the array, and discharge of pumped gasin the dispensing operation, said method comprising: sensing an endpointlimit of the on-stream one of the vessels and switching from theon-stream one of the vessels to another of the vessels in the arrayhaving gas therein, for subsequent dispensing of gas from said anotherof the vessels, as a subsequent on-stream vessel in the dispensingoperation, terminating flow of gas to the pump and inactivating thepump, wherein said terminating and inactivating steps are conductedbetween the step of sensing of the endpoint limit and the switchingstep; and reinitiating flow of gas to the pump and reactivating thepump, wherein said reinitiating and reactivating steps are conductedafter the switching step.
 31. The method of claim 30, wherein theendpoint limit is sensed as an endpoint limit weight of the on-streamone of the vessels.
 32. The method of claim 30, wherein the endpointlimit is sensed as an endpoint limit pressure of gas dispensed from theon-stream one of the vessels.
 33. The method of claim 30, wherein theendpoint limit is sensed as an endpoint limit flow rate of gas dispensedfrom the on-stream one of the vessels.
 34. The method of claim 30,wherein the endpoint limit is sensed as an endpoint limit cumulativevolume of gas dispensed from the on-stream one of the vessels.
 35. Themethod of claim 30, wherein the endpoint limit is sensed as an endpointlimit rate of change of a characteristic of gas dispensed from theon-stream one of the vessels.
 36. The method of claim 30, wherein theendpoint limit is sensed as an endpoint limit dispensing time of gasdispensing from the on-stream one of the vessels.
 37. The method ofclaim 30, further comprising controllably setting a time interval duringwhich flow of gas to the pump is terminated.
 38. The method of claim 30,further comprising dynamically setting a time interval during which flowof gas to the pump is terminated.
 39. The method of claim 38, whereinsaid dynamically setting step comprises use of a proportionalintegrating derivative (PID) control loop.
 40. The method of claim 39,wherein said proportional integrating derivative (PID) control loop isoperatively coupled with a pressure transducer in flow circuitrycoupling the pump in gas flow communication with the array of gasstorage and dispensing vessels.
 41. The method of claim 30, furthercomprising controllably setting a time interval during which the pump isinactivated.
 42. The method of claim 41, further comprising use of atimer.
 43. The method of claim 30, comprising terminating flow of gas tothe pump prior to inactivating the pump.
 44. The method of claim 30,comprising reinitiating flow of gas to the pump prior to reactivatingthe pump.
 45. The method of claim 30, wherein the gas storage anddispensing vessels hold a solid-phase physical adsorbent having sorptiveaffinity for gas stored in and dispensed from the vessels.
 46. Themethod of claim 45, wherein the solid-phase physical adsorbent comprisesa material selected from the group consisting of molecular sieves,carbon, silica, alumina, clays and macroreticulate polymers.
 47. Themethod of claim 45, wherein the solid-phase physical adsorbent comprisescarbon.
 48. The method of claim 30, wherein said gas comprises asemiconductor manufacturing gas.
 49. The method of claim 30, wherein thegas storage and dispensing vessels comprise interiorly disposedregulators.
 50. The method of claim 30, wherein the gas storage anddispensing vessels are disposed in a gas cabinet.
 51. The method ofclaim 50, wherein the gas storage and dispensing vessels are coupled ingas flow communication to a valved manifold in the gas cabinet.
 52. Themethod of claim 51, wherein the pump is contained in a pumper cabinet.53. The method of claim 52, wherein the pumper cabinet further containsa surge tank in pumped gas-receiving relationship to the pump.
 54. Themethod of claim 53, wherein the pump and surge tank are coupled in gasflow communication with a valved manifold in the pumper cabinet.
 55. Themethod of claim 54, wherein the valved manifold in the gas cabinet iscoupled in gas flow communication with the valved manifold in the pumpercabinet.
 56. The method of claim 55, comprising the auto-switchoveroperational sequence including: sensing a vessel empty endpoint limit;generating a corresponding limit sensing signal; switching a switchableactuator in response to said limit sensing signal to a switchedcondition indicative of the limit sensing, and actuating a timer forcounting down a predetermined time interval T1; in response to theswitched condition of the switchable actuator, terminating flow of gasto the pump for a predetermined time interval T2; stalling the pump fora predetermined time interval T3; after expiration of the time intervalT1, switching gas dispensing flow, from a first vessel for which thevessel empty endpoint limit has been sensed, to a second, fresh vessel;dispensing gas from the second, fresh vessel, and at the expiration ofthe time interval T2, flowing gas from the second, fresh vessel to thepump; at the expiration of the time interval T3, reactuating the pump.57. The method of claim 30, wherein gas flow termination to the pump,inactivation of the pump, reinitiation of gas flow to the pump andreactivation of the pump substantially reduces pressure variation ofpumped gas discharged from the pump, in relation to a correspondingvessel switchover not including gas flow termination to the pump,inactivation of the pump, reinitiation of gas flow to the pump andreactivation of the pump in connection with the switchover.
 58. Themethod of claim 57, wherein the pumped gas discharged from the pumpduring the switchover from said first vessel to said second vessel inthe array is characterized by an absence of pressure spike behavior inthe pumped gas.